In the case of series-produced finished parts of concrete, primarily switch cross ties, for the insertion of the component, e.g. tube sockets for the rail, fastening screws in the case of the switch cross ties--an accuracy is required which greatly exceeds that otherwise necessary for construction components. It is an important condition that the component can be fixed in the casing without being displaced during the pouring of the concrete, that the finished part can be removed from the casing, and that the cost of the required steps is low. Besides, the connection of the component with the casing has to be shearable, in order not to impede the movements occurring between the finished part and the casing during the hardening process of the concrete and not to cause damage to the finished part or to the component.
A fastening method is known from German open application 36 29 030 (see also U.S. Pat. No. 4,948,089). This open application further describes various types of fastening devices, consisting basically of a pin and a fastening nipple. The nipple holds the pin in a bore in the casing plate, which determines the position of the component within the finished part. The hollow pin and the nipple can assume various shapes which sometimes are very complicated and thus expensive, shapes. Sometimes, the nipples can be built into the casing only from the less accessible bottom side.